O Ring

O-Rings are torus-shaped (i.e. doughnut-shaped) objects made from elastomeric compounds such as natural or synthetic rubber, and are used to seal mechanical parts against fluid movement (air or liquid).

O-Rings perform their sealing action by deforming to take the shape of their cavity, after being oversized to guarantee a predetermined interference fit.The seal is designed to have a point contact between the o-ring and sealing faces. This allows a high local stress, able to contain high pressure, without exceeding the yield stress of the o-ring body. The flexible nature of o-ring materials accommodates imperfections in the mounting parts. They can withstand fluid pressures upto 100 bar (1500lbs/in2) provided such seals are properly designed and applied. The pressure ratings of the dynamic O-ring seal can be enhanced by using suitable back-up rings. The back-up rings may be of acetal resin, PTFE or Fabric reinforced rubber.

An O-Ring is specified by its inner diameter, cross-section diameter, material hardness/durometer (typically defined by the Shore A hardness), and material composition. "Vijay seals" hold stocks of most commercially available O-Rings in both Metric and Imperial sizes, available in the following materials: - Nitrile Butadiene, Silicone, Poly Tetra Fluro Ethylene (PTFE), Neoprene, Viton (Flurocarbon), Polyurethane, Ethylene Propelene Diene Monomer (EPDM) etc.

O-Ring Characteristics:

The simple geometry is the main characteristic of an 0-Ring which, in conjunction with proper elastomer selection results in a low cost, easy to use and efficient sealing system. Elastomeric materials, when compressed, react like a high viscosity fluid which transmits applied stress in every direction; consequently, the 0-Ring serves as a barrier, blocking the leak paths between the sealing surfaces. Sealing is always achieved through a positive compression or squeezing action, resulting in a deformation of the 0-Ring cross-section. The most important sealing characteristic of an 0-Ring is its resistance to compression set or residual deformation.

Advantages of O-rings:

   * They seal over a wide range of pressure, temperature and tolerance.
    *No critical torque on tightening, therefore unlikely to cause structural damage.
    *Ease of service, no smearing or retightening.
    *O-rings normally require very little room and are light in weight.
   * In many cases an O-ring can be reused, an advantage over non-elastic flat seals and crush-type gaskets.
   * The duration of life in the correct application corresponds to the normal ageing period of the O-ring material.
   * O-ring failure is normally gradual and easily identified.
  *  Where differing amounts of compression effect the seal function (as with flat gaskets), an O-ring is not effected because metal to metal contact      is      generally allowed for.
    *They are cost-effective.